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Oil change and refrigerant Questions for Poodle Head Mikey and Others

You said in a post some time ago that you believe it extends the life of a compressor to change its oil using whatever type oil the compressor carries. If I have this done, will I lose or be able to recover the refrigerant?

Secondly, when I do need to replace my heat pump, should I consider buying a new R-407C unit or just go with the more common R-409A?

Oil in many systems is not filtered in any way.
Oil is composed of chained-together molecules.
Over time the sheering actions involved with the lubrication process 'cut' the molecule chains shorter and shorter. This effect is greater if there are gears involved but it happens in all machines. The shorter molecule chains lubricate less well than when they were longer.
Over periods of time and service oil is sometimes lost.

Now: refrigeration compressors tend to be conservatively designed and applied - so their stresses tend to be low. In comparison to an engine or a gearbox.

Nonetheless; in any compressor over 5-6-7 years old - yes; I believe that changing the oil often benefits the compressor. And . . . . It sure doesn't hurt anything to have the correct of amount of new oil installed in a compressor. <g>

I used to feel otherwise - but after experimenting with compressors and systems and seeing how little dirty oil is often found in some still-running-fine compressors - I've changed my opinion. You can't know for certain what's inside most welded hermetic compressors - unless you put it there yourself.

PHM
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Originally Posted by slydawg

You said in a post some time ago that you believe it extends the life of a compressor to change its oil using whatever type oil the compressor carries. If I have this done, will I lose or be able to recover the refrigerant?

Secondly, when I do need to replace my heat pump, should I consider buying a new R-407C unit or just go with the more common R-409A?

PHM
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The conventional view serves to protect us from the painful job of thinking.

That may be true - not worth the cost I mean. But I am often working either for myself or for reasons other than a substantial profit.

And I'm not advocating that everyone always replace the compressor oil. <g>. I was just answering the man's questions. <g>

And in counter-point to my statements: WTH? Let's face it; maybe changing the compressor oil has never made any difference at all - how would I really Know if they would have just kept running or not? <g>

Not very real-working-world; but recently I changed the oil in a 1978 R-22 compressor. The removed-oil was about 50% of the stated charge volume. (AC application with 16' line run and overhead evap - so it wasn't trapped anywhere) and it looked pretty dark colored. The system hadn't operated for at least the last ten years but seems to be happily purring along now. Of course; maybe it would be with the old low-volume oil charge still in there. Nonetheless; I am happier knowing that my 'antique' compressor has the correct amount of known-good oil in it.

Which reminds me: I started out to change to POE but it was most of $100. A Gallon! So I used mineral oil at about $25. per gallon and added some Supco 88 - maybe 5%. <g>

PHM
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Originally Posted by beenthere

How old is the unit. If its an old R22 unit. Changing oil now, may not be worth the cost.

PHM
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The conventional view serves to protect us from the painful job of thinking.

PHM, I am not understanding the oil not trapped comment. Don't get me wrong I am not doubting what you are saying just trying to get clarification in my own mind.

The evap is above the condenser as I understand, which usually has an inverted trap in the line set to prevent refrig from migration in the off cycle. The evaps usually get fed from the distributor to the bottom row of tubes in the coil slabs and fill up from there with the suction manifold coming off the top row of tubes. So isn't that in essence a big trap? The other question is if only half of the oil was in the compressor and the system has never had a blowout where it would have lost oil, in which case I would have thought you would have added back, where did the oil go?